1. Field of the Invention
The present invention relates to a semiconductor device and a manufacturing method thereof. More specifically, the present invention relates to a semiconductor device capable of enhancing a heat radiation effect from a substrate and to a manufacturing method thereof.
2. Description of the Related Art
In recent years, a high electron mobility transistor (HEMT) has been widespread as a low noise amplifying element. The HEMT is constructed by forming a channel layer, a spacer layer and an electron supply layer in this order on a semiconductor substrate. A flow of a two dimensional electron gas (2DEG) formed on an interface between the channel layer and the spacer layer is controlled by an electric field from a gate electrode, and thus a current amount between a source and a drain is controlled.
There are some types in the HEMT in accordance with compositions of respective semiconductor layers constituting the HEMT. Among them, an AlGaN/GaN heterojunction HEMT including a GaN channel layer and an AlGaN spacer layer is suitable for a high power operation. However, as shown in FIG. 7 of Non-Patent Document 1, in the AlGaN/GaN heterojunction HEMT, when the high power operation is performed, the current amount is reduced due to heat generation of the element, causing a disadvantage in that sufficient element characteristics cannot be obtained. Accordingly, it is essential to take effective solution for this heat radiation problem.
Note that technologies relating to the present invention are also disclosed in Patent Document 1, Patent Document 2, Non-Patent Document 2, and Non-Patent Document 3.
(Patent Document 1)
Japanese Patent Laid-Open No. Hei 10 (1998)-265208
(Patent Document 2)
Japanese Patent Laid-Open No. 2000-31462
(Non-Patent Document 1)
P. P. Ruden, et al., MRS Internet J. Nitride Semicond. Res. 4S1, G6.35 (1999)
(Non-Patent Document 2)
P. Kim, et al., Phys. Rev Lett. 87 (2001) 215502
(Non-Patent Document 3)
M. Kusunoki, et al., Appl. Phys. Lett., 77 (2000) 531
The above-described heat generation is seen not only in a compound semiconductor such as the AlGaN/GaN heterojunction HEMT but also in a silicon-based semiconductor device. It is necessary to find the solution for semiconductor devices in general.